When working with metals, consider black oxide to achieve a blackened firm protective surface. This conversion coating minimizes reflective metal properties and provides mild corrosion resistance. Appropriate for ferrous materials, including steel, stainless steel, copper, brass bronze, cast iron, and copper alloys.
You get a black oxide layer by dipping the part into various chemical treatment tanks and a sealant. A benefit of this coating on precision parts is that it has no significant dimensional measurements. Therefore, your part retains the exact measurements within approximately one µm, or roughly 0.001 mm thick.